WASHINGTON (AP) -- The Trump administration faced growing calls Thursday for a forceful response to violence by Turkish presidential guards on American soil, who were briefly detained this week but then set free. The unseemly incident added to U.S.-Turkish tensions that are being compounded by a growing spat over U.S. war strategy against the Islamic State group in Syria.

The United States said it summoned Turkey's ambassador to the State Department, where the No. 2-ranked U.S. diplomat raised concerns about the security detail for President Recep Tayyip Erdogan's visit to Washington, after they were captured on video violently breaking up a protest. U.S. lawmakers demanded stronger action. The government should "throw their ambassador the hell out" of the country, Republican Sen. John McCain said.

The calls came as the administration conceded it had released two members of Erdogan's detail after holding them briefly after the incident, which took place outside the Turkish ambassador's residence in the U.S. capital on Tuesday. While officials vowed an investigation, the guards are already safely back in Turkey with Erdogan, dampening any prospects for holding them accountable.

Local police and lawmakers initially speculated that diplomatic immunity prevented the U.S. from holding the men. A U.S. official said Thursday that wasn't the case. Instead, Erdogan's guards were released under a globally recognized custom under which nations don't arrest or detain visiting heads of state and members of their delegations, said the official, who wasn't authorized to comment publicly on the matter and requested anonymity.

Continue reading the main story The guards' release left the U.S. struggling to point to anything that amounts to accountability. It also fueled the perception that the U.S. allows Turkey's leader to bring strongman tactics with him when he visits the U.S. capital. Last year, Turkish security officials manhandled several journalists at a Washington think tank where Erdogan was set to speak.

"There must be consequences," Rep. Steny Hoyer, the No. 2 Democrat in the House, said Thursday.

The State Department called the latest incident "deeply disturbing," insisting that a "thorough investigation that will allow us to hold the responsible individuals accountable is of the upmost importance to us."

The fracas erupted as Erdogan arrived at the ambassador's residence following a meeting with President Donald Trump. Videos show people pushing past police to confront a small group of protesters across the street.

Attacking with their fists and feet, men in dark suits and others are seen repeatedly kicking one woman as she lay curled on a sidewalk. Another person wrenches a woman's neck and throws her to the ground. A man with a bullhorn is repeatedly kicked in the face. In all, nine people were hurt.

"This isn't Turkey. This isn't a third-world country," McCain said on MSNBC.

Another video shared on social media Thursday showed Erdogan watching the melee unfold from the backseat of his vehicle. He later exits the vehicle and peers toward the chaos.

Turkey's embassy blamed the violence on demonstrators, saying they aggressively provoked Turkish-American citizens gathered to see Erdogan. The embassy alleged, without evidence, that the demonstrators were associated with the Kurdistan Workers' Party, or PKK, which has waged a three-decade-long insurgency against Turkey and is considered a terrorist group by the United States.

The violent capstone to Erdogan's visit spoke to the sky-high tensions between the U.S. and Turkey, NATO allies that have increasingly sparred over U.S. strategy toward defeating IS militants in Syria.

To Turkey's dismay, Trump has decided to arm Syrian Kurdish militants in the impending fight to retake the key city of Raqqa. Washington considers the Syrian Kurds an effective force against IS. Turkey sees them as a PKK extension and existential threat to Turkish sovereignty.

In its protest against Trump's decision, Turkey's foreign minister demanded Thursday that Trump dismiss the U.S. envoy in charge of the anti-IS coalition, Brett McGurk.

And Erdogan, speaking in Istanbul two days after meeting Trump, said he was putting Washington on notice that his forces won't hesitate to attack U.S.-backed Kurds if they threaten Turkey.

"We are already telling you in advance: Our rules of engagement give us this authority," Erdogan said. "We will take such a step and we won't discuss it or consult with anyone."

The Trump administration rushed to McGurk's defense.

State Department spokeswoman Heather Nauert said McGurk has "the full support and backing" of Trump and Secretary of State Rex Tillerson.

Still, Nauert sought to acknowledge Turkey's misgivings about terrorism by the PKK and other groups.

"We respect those concerns, and continue regular consultations with our NATO ally on this and other topics of mutual importance," Nauert said.

Associated Press writers Zeynep Bilginsoy in Istanbul and Jessica Gresko in Washington contributed to this report.